Tonegawa Susumu

Tonegawa Susumu, born in 1939, Japanese molecular biologist at the Massachusetts Institute of Technology (MIT) and sole winner of the 1987 Nobel Prize in physiology or medicine. Tonegawa was born in Nagoya and educated at Kyōto University and at the University of California at San Diego, from which he received his doctorate in 1969. He began research on antibodies at the Basel Institute for Immunology in Switzerland in 1971 and 10 years later returned to MIT as a full professor.

Tonegawa's Nobel Prize recognized him for his discovery of how as many as 1 billion different specific antibodies can come from what are at most 1000 possible gene segments in the cells responsible for antibody formation in humans and other vertebrates. Antibodies are Y-shaped protein molecules and consist of two amino-acid chains combined. Foreign substances, such as viral or bacterial infections, called antigens, invade the body and are fought off by antibodies, which attack and cling to the antigens by the tips of the branches of the Y. Only certain antibodies (depending on the way the amino acids have combined) can adhere to certain antigens; the fit must be exact. Scientists knew that antibodies originate in white blood cells that are classified as B lymphocytes (or B cells). They also knew that there were a limited number of genes within a B cell and therefore could not figure out how so many more antibodies could be produced than the number of genes in the B cells. When Tonegawa discovered that the constant shuffling and recombining of genetic material as the cell grows results in many new genes in each cell, he had the answer.